Hi
That's a very nice looking trailer !!!
I do understand the desire to "keep it original". Toilets and electrical have come a *long* way since
1957. Step back a bit and take a look at the modern options for toilets that may eliminate the black tank. I'm not saying they are the only solution, just that now is the time to do the research. You *will* need a gray water tank as well on the "new" trailer....
On the electrical side, modern converter / chargers and LED lighting is *way* ahead of what they had "back then". Again, not a "must do", but something to dig into and think about.
Plumbing and electrical, for the most part, are hidden away once the renovations are done. You can still have the "look and feel" of a classic, without it actually being 100% classic. For some that is bunk and yes, I get it. For others, it works.
Decisions !!!!
Bob